1. Field of the Invention
This invention relates to a tire pneumatic pressure detector capable of detecting blowout of a tire or the degree of the drop of its pneumatic pressure.
2. Description of the Related Art
A tire pneumatic pressure detector according to the prior art detects blowout of a tire or the drop its pneumatic pressure, and raises an alarm, to a driver, by turning on an alarm lamp (e.g. Japanese Unexamined Patent Publication (Kokai) No. 10-71819).
However, detectors that raise an alarm in accordance with the blowout of the tire or the degree of the drop of the pneumatic pressure have not yet been known, and the driver cannot judge the degrees of blowout of the tire and the drop of the pneumatic pressure. Particularly in the case of a so-called xe2x80x9crun-flat tirexe2x80x9d, a vehicle can run to a certain extent even when the pneumatic pressure drops to zero. However, as the vehicle naturally cannot run unlimitedly, it is preferred for the driver to know the degree of blowout or how much more the vehicle can run.
On the other hand, it is possible to collect data of running of the vehicle after blowout of the tire or the drop of its pneumatic pressure under a test condition (data representing the relation between a running distance after blowout of the tire and the tire condition after its blowout), but data under the practical use condition by users in general (hereinafter called the xe2x80x9cmarket dataxe2x80x9d) have not yet been collected.
In view of the background described above, it is an object of the present invention to make it possible to judge the degrees of blowout of a tire and the drop of its pneumatic pressure.
It is another object of the present invention to make it possible to collect the market data during running after blowout of the tire or after the drop of its pneumatic pressure.
According to a first aspect of the present invention for accomplishing the objects described above, there is provided a tire pneumatic pressure detector comprising tire pneumatic pressure detection means for detecting a tire pneumatic pressure; pneumatic pressure drop detection means for comparing the tire pneumatic pressure detected by the tire pneumatic pressure detection means with a predetermined value, and detecting the drop of the tire pneumatic pressure when the tire pneumatic pressure is lower than the predetermined value; and first memory means for storing data about a timing at which the drop of the tire pneumatic pressure occurs.
Because the first memory means stores the timing at which the drop of the tire pneumatic pressure occurs, the degrees of blowout and the drop of the pneumatic pressure can be judged on the basis of this timing.
According to a second aspect of the present invention, there is provided the tire pneumatic pressure detector described above, which further comprises second memory means for storing the lapse of time from the timing at which the drop of the tire pneumatic pressure occurs, or data about a running distance from this timing. In this way, the degrees of blowout and the drop of the pneumatic pressure can be judged from the lapse of time and the running distance.
According to a third aspect of the present invention, there is provided a tire pneumatic pressure detector which further comprises an alarm for warning the drop of the tire pneumatic pressure when the drop of the tire pneumatic pressure occurs, wherein the alarm changes the warning method in accordance with the data stored in the second memory means. Consequently, the driver can judge the degrees of blowout and the drop of the pneumatic pressure. More concretely, as represented by a fourth aspect of the present invention, a flashing frequency of an alarm lamp may be set to a higher frequency for a longer lapse of time or a longer running distance than a shorter lapse or time or a shorter running distance.
According to a fifth aspect of the present invention, the tire pneumatic pressure detector described above further comprises switching number of times detection means for detecting a switching number of times of ON/OFF of an ignition switch, wherein, when the number a of times of switching detected by the switching number of times detection means is greater than a predetermined number of times when the tire pneumatic pressure drop detection means detects that the tire pneumatic pressure is higher than the predetermined value, the data stored in the second memory means is cleared. According to this construction, it becomes possible to prevent the data stored in the second memory means from being readily cleared by the chattering of the tire pneumatic pressure judgment value very close to the threshold level of warning.
According to a sixth aspect of the present invention, the tire pneumatic pressure detector described above has its feature in that when a fault diagnosing device inputs a fault diagnosing signal, the lapse of time from the timing at which the drop of the tire pneumatic pressure occurs or the data about the running distance from the timing, each stored in the second memory means, is outputted to the fault diagnosing device. When the fault diagnosing device can read out the data stored in the second memory means, the market data about blowout of the tire and about running after the drop of the air pressure can be acquired through the fault diagnosing device when the tire is exchanged in a service station, for example.
The means described above represent concrete means described in the later-appearing embodiment of the invention.